This type of conventional projector apparatuses are equipped with a lamp serving as a light source and an optical system having such elements as a polarization beam splitter, polarization plates, liquid crystal panels (LCPs), and a projection lens, all housed in a casing. Provided on a wall of the casing is an exhaust unit adapted to create an air flow inside the casing to suppress temperature rise in the casing. (See for example, Japanese Patent Application Laid Open No. H8-275096.)
However, since the exhaust unit is orientated to the hot lamp so as to inspire air heated by the lamp, the air discharged from the exhaust unit is heated to a high temperature, which makes the user of the projector unpleasant when he is exposed to the hot air. Hence, in order to lower the temperature of the exhausted air, the exhaust fan of the exhaust unit must be operated at a high speed, which in turn creates a bothering noise.
In the market of portable projector apparatuses, low-cost competition is very severe, so that, in order to respond to a wide range of demands in the market, manufacturers often develop different models derived from the original basic model shortly after issuing the basic model to the market. In designing an improved model having a greater lighting intensity, designers are required to make an attempt to utilize as many elements of the basic model as possible in order to reduce the cost and development cycle for the new model. When the lighting intensity is increased in the new model, a designer will be motivated to add only local or minor changes to the existing cooling system to provide the new model with additional and sufficient cooling power, without altering its basic structure.